<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./vuejs/vue.js"></script>
</head>
<body>
    <style>
        .fade-enter, .fade-leave-to{
            opacity: 0;
        }
        .fade-enter-active, .fade-leave-active{
            transition: opacity .5s;
        }


    </style>
    <div id="app">
        <transition name="fade" mode="out-in">
            <button v-bind:key="isOff" @click="isOff = !isOff">{{isOff?'Off':'on'}} </button>
        </transition>
    </div>
    <script>
        var vm  = new Vue({
            el:'#app',
            data:{
                isOff:true
            }
        });


    </script>
</body>
</html>